1. Field of the Invention
The present invention relates to a high zoom-ratio zoom lens system having a favorable high zoom-ratio exceeding 13:1 for use in a single-lens reflex (SLR) camera, and especially for use in a digital SLR camera.
2. Description of Related Art
As examples of a high zoom-ratio zoom lens system having a zoom ratio exceeding 10:1 to 13:1, a four-lens-group zoom lens system including a positive lens group, a negative lens group, a positive lens group and a positive lens group, in this order from the object, and a five-lens-group zoom lens system including a positive lens group, a negative lens group, a positive lens group, a negative lens group and a positive lens group, in this order from the object, are known in the art. These zoom lens systems are proposed in, for example, Japanese Unexamined Patent Publication Nos. 2008-304952, 2006-284763, 2006-106191, and 2008-3195.
In the high zoom-ratio zoom lens system taught in Japanese Unexamined Patent Publication Nos. 2008-304952, 2006-284763 and 2006-106191, the zoom ratio is approximately 10:1, and the focal length at the long focal length extremity is approximately 200 mm, which is somewhat short.
In the high zoom-ratio zoom lens system taught in Japanese Unexamined Patent Publication No. 2008-3195, the zoom ratio is approximately 13:1; however, the focal length at the long focal length extremity is approximately 250 mm, and the f-number is 6.3, which is slow.